1. Field of the Invention
The invention relates hydro-pneumatic spring struts and more particularly, to a self-pumping hydro-pneumatic spring strut with internal leveling.
2. Description of the Related Art
Spring struts of this kind are already known (for example, DE 33 06 393 C1), in which the throttle is formed by an orifice between a valve body of the suction valve and that end face of a sleeve which faces said valve body. Between the throttle and the bleed orifice, the inner wall of the pump rod is utilized as a bleed duct. Pressure equalization between the high-pressure chamber and the low-pressure chamber takes place, initially, via the relatively large bleed orifice insensitive to dirt, along the bleed duct, through the throttle and, from there, centrally through the pump rod. Since the throttle is mounted between the suction valve plate and the end-face valve seat of the sleeve, there is virtually no risk of the throttle being clogged by particles in the damping medium. This is due to the valve plate being lifted from its seat, which results in the throttle being opened constantly and being flushed free by the damping medium. However, a design of this type is complicated and the individual pump rod lengths, together with their sleeves of correspondingly differing length, in each case have to be adapted to the overall length of the spring strut. This means that, in different instances of use, spring struts of different length are also employed, which in each case require a corresponding pump rod. Furthermore, the dimensional accuracy of the sleeve and of its receiving bore in the pump rod must be made perfect, and, since the valve plate which, together with the end face of the pump rod, forms the control edges, re-machining or cutting of the control edges is necessary after the sleeve has been installed in the pump rod.